The present invention relates to a cooling device for dumping the heat generated by a travelling-wave tube (TWT) of high power (generally more than 100 W at radiofrequency) of the kind mounted on telecommunications satellites.
Maintaining a travelling-wave tube at a temperature compatible with long lifetime is complicated by the special conditions encountered in space applications, where cooling can hardly be done otherwise than by radiating to black space, and where constraints on bulk and weight are very severe.
At present, use is made in particular of a cooling device that includes thermal link means from the tube collector (which generates about 90% of the total thermal power of the travelling-wave tube) to means for radiating the heat to space that are constituted by the general radiator of the satellite. However, under such circumstances, the radiator must be dimensioned so as to maintain all of the parts to which it is connected at the lowest of the temperatures required by any of the parts, which is generally less than 75.degree. C. This requires the radiator to have a large radiating area.
Another solution, which makes allowance for the fact that the collector can tolerate a high temperature, greater than 200.degree. C., consists in thermally insulating the collector from the remainder of the tube and in providing it with a cowling or cover or with a structure having radial fins, the cowling or the fins radiating directly into black space. Since the cowling or the radiating structure must be external, whereas the tube is internal, the tube must be mounted at the margin of the equipment-carrying panel (i.e. north or south panel for a platform that is stabilized about three axes). That solution which restricts the mounting area for TWTs to the margin of the panel requires the satellite to be given dimensions that are greater than required while the central portion is left unused. Furthermore, that generally requires long electrical and radiofrequency connections, in particular because the antennae also have to occupy predetermined positions.